Aircraft Turbochargers, Wastegates, Controllers & Valves

As Hartzell Engine Technologies' (HET) exclusive distribution agreement with Aviall is coming to an end on February 28th 2014, HET will be moving
to a much broader distribution network that now includes the appointment of Quality Aircraft Accessories (QAA) as a Recommended Service Facility
(RSF) for turbochargers, wastegates, controllers, and pressure relief valves.

Use our catalog search below, or call us at 1-877-833-6948 to check price and availability. Need it fast? Ask about our one day service!

How a Turbocharger works

Most aircraft piston engines are manufactured by Lycoming or Continental Motors. These engines consume gases that are drawn into the engine by
the downward stroke of the piston (producing a low-pressure area). The amount of air consumed, compared to the theoretical volume of air consumed
if the engine could sustain atmospheric pressure, is called volumetric efficiency. The main function of a turbocharger is to increase the engine’s
volumetric efficiency; this may be accomplished by increasing the intake gas density (typically air).

The compressor of a turbocharger draws in ambient air. The air is then compressed before entering the intake manifold at a greater pressure. This
results in a greater mass of air entering the cylinders with each intake stroke. The kinetic energy derived from the engine’s exhaust gases
then spins the centrifugal compressor.

A turbocharger utilizes an array of controllers to regulate air flow. This system has become very complex and evolved considerably over the last
100 years. Modern turbochargers may use a combination of the following: variable absolute pressure controllers (VAPC), absolute pressure controllers
(APC), density controllers, differential pressure controllers, sloped controllers, rate controllers, pressure ratio controllers, wastegates,
and pressure relief valves.

Breakdown of a Turbocharger

The turbocharged induction system mechanisms are similar to a normally aspirated system but with the addition of a turbocharger and turbocharger
controllers. The location of the turbocharger itself is between the air intake and the fuel metering unit. A typical turbocharger consists
of a solitary rotating shaft with a centrifugal compressor impeller mounted on one side and a small radial turbine fixed to the other side.
Both the impeller (cold section) and turbine (hot section) are individual housings joined by a common bearing housing which contains two aluminum
bearings that support the center shaft. In this configuration, the exhaust gas spins the turbine which translates the centripetal energy through
the common shaft to the impeller. The impeller then draws in air and compresses it.

On a standard single engine aircraft the air comes in through an air intake located below the propeller. From there air is ducted to the turbocharger
at the back of the engine. The turbocharger compresses the intake air and sends the newly compressed air to the air metering section of the
fuel metering device. Once the air is metered it is ducted to the intake manifold through the cylinder intake valves where the air is then
mixed with a metered amount of fuel.

In addition to the friction produced by high gyratory speeds, the exhaust gases ducted through the turbine heat the turbocharger. The turbine inlet
temperature may get as high as 1,600⁰F, because of this there needs to be a large flow of oil keeping the bearings within a safe operating
temperature. Therefore, a constant flow of engine oil, approximately four to five gallons of oil per minute, must be pumped through the bearing
housing to cool and lubricate the bearings.

Wastegates function to regulate the power output of the turbocharger system. By controlling exhaust airflow, aircraft wastegates manage the turbine
speed, and therefore the compressor housing intake. A series of aircraft controllers function as the brain behind the wastegate. At varying
speeds, altitude, engine power, and air pressure, a variety of controllers keep the turbocharger system at equilibrium.

Preventative Maintenance on a Turbocharger

Maintenance on a turbocharger is critical to obtain a long and hassle free service life. A turbocharger must regularly withstand extreme operating
conditions –with exhaust inlet temperatures exceeding 1600° F and the turbine wheel rotating at over 90,000 RPM. Turbine and compression wheel
blades must be carefully inspected for any cracks or damage caused by foreign object debris. It is also important to turn the wheels by hand
and inspect for any drag or rubbing against the housing. One of the most important processes in the turbocharger is the lubrication system,
which is provided by the aircraft engine oil. Oil contamination, foreign object debris, and oil supply problems are the most frequent reasons
for premature turbocharger failure and can lead to overheating of the bearings and the center housing.

Turbocharging System

Suggested Resources:

Looking for more information on aircraft turbochargers and turbocharger systems? Check out some of the helpful links below.

Service Bulletins

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